kdump broken on 2.6.37-rc4

[Yinghai Lu]

On 12/08/2010 06:19 AM, Stanislaw Gruszka wrote:
> On Tue, Dec 07, 2010 at 11:24:46AM -0800, Yinghai Lu wrote:
>> On 12/07/2010 02:50 AM, Stanislaw Gruszka wrote:
>>> On Fri, Dec 03, 2010 at 12:54:01PM -0500, Neil Horman wrote:
>>>> On Fri, Dec 03, 2010 at 06:11:48PM +0100, Stanislaw Gruszka wrote:
>>>>> On Fri, Dec 03, 2010 at 06:46:09PM +0300, Maxim Uvarov wrote:
>>>>>> 2010/12/3 Stanislaw Gruszka <sgruszka at redhat.com>:
>>>>>>> On my T-60 laptop, i686 system with 2.6.37-rc4 kernel,
>>>>>>> "echo c > /proc/sysrq-trigger" just hung the system. Kdump
>>>>>>> works on 2.6.36. Is this known issue? If not, what info
>>>>>>> I should provide to solve it (I think the easiest way
>>>>>>> to solve the problem would be bisect) ?
>>>>>>>
>>>>>>> Stanislaw
>>>>>>>
>>>>>>
>>>>>> I tested x86 QEMU yesterday with the latest git. It worked.
>>>>>> Might be something target specific.., What does console print?
>>>>>
>>>>> Here is the photo 
>>>>> http://people.redhat.com/sgruszka/20101203_005.jpg
>>>>>
>>>>> There are two BUGs, first "sleeping function called from invalid
>>>>> context" and then "unable to handle null pointer dereference".
>>>>>
>>>> The warning about sleeping is an artifact of the fact that we panic the box with
>>>> irqs disabled I think (although I would think the fault handler would have
>>>> re-enabled them properly).  Not sure what the NULL pointer is from
>>>
>>> NULL pointer dereferece is ok, that's the way sysrq_handle_crash
>>> trigger a crash. Problem here is that secondary kdump kernel hung at
>>> start.
>>>
>>> Bisection shows that bad commit is
>>>
>>> commit 72d7c3b33c980843e756681fb4867dc1efd62a76
>>> Author: Yinghai Lu <yinghai at kernel.org>
>>> Date:   Wed Aug 25 13:39:17 2010 -0700
>>
>> please check debug patches, and boot first kernel and kexec second kernel with "ignore_loglevel debug earlyprintk...."
> 
> Second kernel does not print anything, so maybe it not even start.
> Dmesg from primary kernel attached.
> 
> Stanislaw


please try attached debug patch.

Thanks

	Yinghai
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